The present invention relates to a method and apparatus for inspecting an end face of a nuclear fuel pellet at the center of which a spherical dish or recess is formed, and in particular to a method and apparatus of a type which picks up an image of the pellet end face and judges the quality of the pellet based on this image.
When an image of a pellet end face with a spherical dish is picked up by emission of a parallel beam of light to the pellet end face, the image obtained will have a dark portion around the dish. Therefore, when the obtained image is processed into a binary image, It is difficult to distinguish the dish from defects such as chipping.
Japanese Patent Application, First (A) Publication No. 1136053, describes a method which circumvents the aforesaid problem by adding correction data from a standard image upon processing of the picked-up image into a binary image. This method is, indeed, effective on the assumption that images of the specimens are picked up in a manner similar to the standard image. However, this assumption is often not applicable in practice. In addition, due to the undue load on image processing, inspection is time-consuming, so that high speed inspection of pellet end faces has not been attained.